This invention relates to a shim of a novel shape used for a cable clamp composed of a wedge-like member and a sleeve-like member, those members being telescopically assembled to clamp a cable therebetween through a wedge action, or a longitudinal relative move thereof. In these sorts of clamps, while a shim plate is ordinarily located between the bottom plate of the wedge-like member and the cable prior to the wedge action to effect the action smoothly, it, heretofore, has been a part separated from other two members, therefor, the clamping worker has been caused to set properly the three separate parts in the course of clamping work which results in making the clamping work troublesome and complicated one. The conventional shim 7 is shown in FIG. 5.